1. Field of Invention
This invention relates to methods and systems for undercolor reduction.
2. Description of Related Art
When marking an image in which black text or other dark features are superimposed on a colored background, it is often desirable to first mark the colored background and then mark the text or other dark features on top of the background marking material. This eliminates or masks any mis-registration of the text or other dark features with respect to the background.
However, simply overmarking the text or other dark features on top of the background marking material can result in an excessive build-up of marking material on a marking substrate, which in turn causes marking material transfer problems and/or problems with the marking substrate, such as paper cockling and/or curling when the marking substrate is paper.
To alleviate these problems, undercolor reduction methods have been introduced, in which a reduced amount of background marking material is applied to areas that are to be overmarked. Examples of such methods are set forth in U.S. Pat. Nos. 5,687,303, 5,649,071, 5,635,967, 5,563,985, 5,519,815 and 5,515,479, each incorporated herein by reference in its entirety.
In these methods, a temporary record is kept of each color separation bitmap of an image to be marked so that, prior to actual marking, locations where a black marking material is to be marked over one or more of cyan, magenta and yellow marking materials are known. Data for colors underlying the black marking material can then be modified so that a reduced amount of these underlying colors are marked on the marking substrate.